Clean up usage of icache_disable/dcache_disable

There is no point in disabling the icache on 7xx/74xx/86xx parts and not
also flushing the icache.  All callers of invalidate_l1_instruction_cache()
call icache_disable() right after.  Make it so icache_disable() calls
invalidate_l1_instruction_cache() for us.

Also, dcache_disable() already calls dcache_flush() so there is no point
in the explicit calls of dcache_flush().

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/cpu/74xx_7xx/cache.S b/cpu/74xx_7xx/cache.S
index 3a745cb..eac4544 100644
--- a/cpu/74xx_7xx/cache.S
+++ b/cpu/74xx_7xx/cache.S
@@ -245,6 +245,10 @@
  * Disable L1 Instruction cache
  */
 _GLOBAL(icache_disable)
+	mflr	r4
+	bl	invalidate_l1_instruction_cache		/* uses r3 */
+	sync
+	mtlr	r4
 	mfspr	r3, HID0
 	li	r5, 0
 	ori	r5, r5, HID0_ICE